Please help me I do not know how to answer this.

a.   mass number from atomic number

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.

the only real purpose of sputnik 1 was to beat the us into space. we were getting close to launching a useful satellite, explorer 1 - which launched on january 31, 1958. the ussr had to beat that, so they launched sputnik 1 on october 4, 19